lx279

   / lx279 #1  

dodgee34

New member
Joined
Jan 3, 2016
Messages
1
Location
new zealand
Tractor
john deere lx279
my lx279 just stopped whilst mowing, traced it to a blown fuse, problem it blows as soon as you turn on the ignition have disconnected all engine wiring at senders ect still blowsi disconnected a plug that runs back to the ignition swich just in front of the battery fuse didnt blow traced wiring to a circuit board but cannot detect anything wrong any any ideas appreciated cheers paul
 
   / lx279 #2  
What fuse is blowing? See attached photo.

Appearently there are only two fuses on the circuit board. The starter fuse and headlight fuse.
 

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  • LX279 FUSE.JPG
    LX279 FUSE.JPG
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   / lx279 #3  
On many small tractors a special diode is incorporated into the wiring harness. Typically called a flyback diode.
Its job is to block what is called back electromotive force, generated by things like the coil in a starter solenoid which sends a pulse of high voltage backwards into the electrical system as it shuts off.
If for example the battery was boosted and the cables, even momentarily, connected backwards this diode can be blown.
Once the diode is blown it becomes a dead short in the main electrical system.
I have seen a Kawasaki engine, which is what you have, installed on a Toro zero turn and the flyback diode was blown when a new battery was installed with the cables reversed.
Locating and then removing the diode for a short time will confirm if this is the cause as a new fuse will no longer blow.
If handy you can buy a suitable diode at a big electronics place and cut open the factory rubber case and solder it in.
Here is a Kohler wiring diagram showing the flyback diode. Other engine makes are similar.
Ar3hHCl.jpg


The following picture shows the factory diode cut open to expose the internal electronic component.
It looks like a two pin trailer wiring harness type connector that just plugs into the wiring harness.
Sorry my photo is not clearer.
aBhLOlU.jpg


If you decide to replace the diode you need to take great care to respect the polarity on the new diode so that it matches the old one.

This diode cost about $6. It is higher rated than factory one which is fine.

tNAgku5.jpg

RgJD8Hj.jpg

KOYeHvs.jpg

zoMzWMm.jpg


Dave M7040
 
   / lx279 #5  
Paul hasn't been back since the day he posted the OP. Hope it is fixed.
 
   / lx279 #6  
On many small tractors a special diode is incorporated into the wiring harness. Typically called a flyback diode.
Its job is to block what is called back electromotive force, generated by things like the coil in a starter solenoid which sends a pulse of high voltage backwards into the electrical system as it shuts off.
If for example the battery was boosted and the cables, even momentarily, connected backwards this diode can be blown.
Once the diode is blown it becomes a dead short in the main electrical system.
I have seen a Kawasaki engine, which is what you have, installed on a Toro zero turn and the flyback diode was blown when a new battery was installed with the cables reversed.
Locating and then removing the diode for a short time will confirm if this is the cause as a new fuse will no longer blow.
If handy you can buy a suitable diode at a big electronics place and cut open the factory rubber case and solder it in.
Here is a Kohler wiring diagram showing the flyback diode. Other engine makes are similar.
Ar3hHCl.jpg


The following picture shows the factory diode cut open to expose the internal electronic component.
It looks like a two pin trailer wiring harness type connector that just plugs into the wiring harness.
Sorry my photo is not clearer.
aBhLOlU.jpg


If you decide to replace the diode you need to take great care to respect the polarity on the new diode so that it matches the old one.

This diode cost about $6. It is higher rated than factory one which is fine.

tNAgku5.jpg

RgJD8Hj.jpg

KOYeHvs.jpg

zoMzWMm.jpg


Dave M7040

Do you know if the John Deere LX279 with a Kawasaki engine has this diode?. Im thinking of replaceing the circuit board/ MY tractor is dead. charged battery ignition lights all turn on correctly when I turn the key but not even a click from the fuel solenmoid. Doesnt turn over at all.
 
   / lx279 #7  
thebeorn
Have you checked all connections to the battery? Have you had the battery load tested?
 
   / lx279 #8  
thebeorn
Have you checked all connections to the battery? Have you had the battery load tested?
Hi @beenthere I have the same issue. However, if I jump the starter solenoid to the battery, the starter starts the engine fine. I have switch out the key switch and board from another mower but the issue remains. I have a feeling there's a diode somewhere in the wirirng loom but cannot locate it. Any ideas?
 
   / lx279 #9  
The OP stated that when he went to start, the fuse would blow. Are you having that same trouble ?
 
   / lx279 #10  
The OP stated that when he went to start, the fuse would blow. Are you having that same trouble ?
No, the fuse is fine. Just no click from the starter solenoid when key is turned to start. PTO is not engaged, brake and seat switch are engaged. However, if I jump the starter solenoid to the battery, the starter starts the engine which runs fine.
 
 
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